AIM: To evaluate the incidence and risk factors of hypotony in patients with blunt ocular trauma. METHODS: The medical records of 145 patients with blunt ocular trauma were reviewed. Hypotony was defined as an average intraocular pressure (IOP) of 5mmHg or less for three times. RESULTS: Among these 145 patients, hypotony was noted in 10 (6.9%) patients. The rate of hypotony in patients with ciliochoroidal detachment was 66.7% (2 out of 3 eyes), and 5.6% (8 out of 142 eyes) in patients without ciliochoroidal detachment，the difference was statistically significant（P=0.003）. The rate of hypotony in patients with traumatic retinal detachment was 18.5% (5 out of 27 eyes), and 4.2% (5 out of 118 eyes) in patients without traumatic retinal detachment, the difference was statistically significant (P=0.026). The rate of hypotony in the patients with anterior proliferative vitreoretinopathy was 42.9% (3 out of 7 eyes) and 5.1% (7 out of 138 eyes) in the patients without anterior proliferative vitreoretinopathy, the difference was statistically significant（P=0.002）. CONCLUSION: Ocular hypotension is a complication of blunt ocular trauma. The risk factors include ciliochoroidal detachment, traumatic retinal detachment, and anterior proliferative vitreoretinopathy.